The pharmacokinetics of midazolam in man

Midazolam Boosting With Cobicistat in a Patient With Drug-Resistant Epilepsy and Focal Status Epilepticus

BACKGROUND

This report presents the case of a patient with drug-resistant epilepsy. Despite treatment with 4 antiepileptic drugs, the patient experienced an increasing frequency of focal seizures, necessitating hospitalization, and continuous intravenous midazolam infusion.

METHODS

Cobicistat was introduced as a pharmacokinetic booster to decrease the metabolic clearance of midazolam, leading to increased exposure and an extended half-life.

RESULTS

Cobicistat boosting allowed the switch from intravenous to oral midazolam, and the patient was discharged on an oral midazolam regimen.

CONCLUSIONS

Cobicistat can be effectively used to boost midazolam exposure pharmacokinetically in patients with drug-resistant epilepsy who require stable midazolam blood concentrations.

Prediction of Pharmacokinetics for CYP3A4-Metabolized Drugs in Pediatrics and Geriatrics Using Dynamic Age-Dependent Physiologically Based Pharmacokinetic Models

Background/Objectives: The use of medicines in pediatrics and geriatrics is widespread. However, information on pharmacokinetics of therapeutic drugs mainly comes from healthy adults, and the pharmacokinetic parameters of therapeutic drugs in other age stages, including pediatrics and geriatrics, are limited. The aim of the study was to develop a dynamic age-dependent physiologically based pharmacokinetic (PBPK) model to predict the pharmacokinetics of drugs in humans at different ages. Method: The PBPK models characterizing dynamic age-dependence were developed in adults (20-59 years old) and 1000 virtual individuals were constructed. Four CYP3A substrates, namely midazolam, fentanyl, alfentanil and sufentanil, served as model drugs. Following validation using clinic observations in adult populations, the developed PBPK models were extrapolated to other age populations, such as pediatrics and geriatrics, via replacing their physiological parameters and pharmacokinetic parameters, such as organ volume, organ blood flow, clearance, fu,b and Kt:p. The simulations were compared with clinic observations in corresponding age populations. Midazolam served as an example, the dose transitions between adult pediatrics and adult geriatrics were visualized using the developed PBPK models. Results: Most of observed plasma concentrations fell within the 5th-95th percentile of the predicted values in the 1000 virtual individuals, and the predicted AUC0-t and Cmax were almost within between 0.5 and 2 times of the observations. The optimization of dosages in pediatrics and geriatrics were further documented. Conclusions: The developed PBPK model may be successfully used to predict the pharmacokinetics of CYP3A4-metabolized drugs in different age groups and to optimize their dosage regiments in pediatrics and geriatrics.

Towards More Robust Evaluation of the Predictive Performance of Physiologically Based Pharmacokinetic Models: Using Confidence Intervals to Support Use of Model-Informed Dosing in Clinical Care

BACKGROUND AND OBJECTIVE

With the rise in the use of physiologically based pharmacokinetic (PBPK) modeling over the past decade, the use of PBPK modeling to underpin drug dosing for off-label use in clinical care has become an attractive option. In order to use PBPK models for high-impact decisions, thorough qualification and validation of the model is essential to gain enough confidence in model performance. Currently, there is no agreed method for model acceptance, while clinicians demand a clear measure of model performance before considering implementing PBPK model-informed dosing. We aim to bridge this gap and propose the use of a confidence interval for the predicted-to-observed geometric mean ratio with predefined boundaries. This approach is similar to currently accepted bioequivalence testing procedures and can aid in improved model credibility and acceptance.

METHODS

Two different methods to construct a confidence interval are outlined, depending on whether individual observations or aggregate data are available from the clinical comparator data sets. The two testing procedures are demonstrated for an example evaluation of a midazolam PBPK model. In addition, a simulation study is performed to demonstrate the difference between the twofold criterion and our proposed method.

RESULTS

Using midazolam adult pharmacokinetic data, we demonstrated that creating a confidence interval yields more robust evaluation of the model than a point estimate, such as the commonly used twofold acceptance criterion. Additionally, we showed that the use of individual predictions can reduce the number of required test subjects. Furthermore, an easy-to-implement software tool was developed and is provided to make our proposed method more accessible.

CONCLUSIONS

With this method, we aim to provide a tool to further increase confidence in PBPK model performance and facilitate its use for directly informing drug dosing in clinical care.

Structural Modification in Anesthetic Drug Development for Prodrugs and Soft Drugs

Among the advancements in drug structural modifications, the increased focus on drug metabolic and pharmacokinetic properties in the anesthetic drug design process has led to significant developments. Drug metabolism also plays a key role in optimizing the pharmacokinetics, pharmacodynamics, and safety of drug molecules. Thus, in the field of anesthesiology, the applications of pharmacokinetic strategies are discussed in the context of sedatives, analgesics, and muscle relaxants. In this review, we summarize two approaches for structural optimization to develop anesthetic drugs, by designing prodrugs and soft drugs. Drugs that both failed and succeeded during the developmental stage are highlighted to illustrate how drug metabolism and pharmacokinetic optimization strategies may help improve their physical and chemical properties.

Effect of sedative premedication with oral midazolam on postanesthesia care unit delirium in older adults: a secondary analysis following an uncontrolled before-after design

BACKGROUND

Sedative premedication with benzodiazepines has been linked with prolonged recovery and inadequate emergence during the immediate postoperative period. We aimed to analyze the association between postanesthesia care unit (PACU) delirium and sedative premedication with oral midazolam.

METHODS

We performed a secondary analysis of prospectively collected data before (midazolam cohort) and after (non-midazolam cohort) implementation of a restrictive strategy for oral premedication with midazolam. From March 2015 until July 2018, we included patients 60 years and older, who underwent elective radical prostatectomy for prostate cancer. Exclusion criteria were contraindications to premedication with midazolam, preoperative anxiety, and a history of neurological disorders. Patients, who were scheduled for postoperative admission to the intensive care unit, were excluded. Between 2015 and 2016, patients received 7.5 mg oral midazolam preoperatively (midazolam cohort). Patients included between 2017 and 2018 did not receive any sedative medication preoperatively (non-midazolam cohort). The primary endpoint was the incidence of PACU delirium.

RESULTS

PACU delirium rates were 49% in the midazolam cohort (n = 214) and 33% in the non-midazolam cohort (n = 218). This difference was not statistically significant on multivariable logistic regression analysis (OR 0.847 [95% CI 0.164; 4.367]; P = 0.842). Age (OR 1.102 [95% CI 1.050; 1.156]; P < 0.001), the cumulative dose of sufentanil (OR 1.014 [95% CI 1.005; 1.024]; P = 0.005), and propofol-sufentanil for anesthesia maintenance (OR 2.805 [95% CI 1.497; 5.256]; P = 0.001) were significantly associated with PACU delirium.

CONCLUSION

Midazolam for sedative premedication was not significantly associated with PACU delirium. The reduction in the incidence of PACU delirium throughout the study period may be attributable to improvements in perioperative management other than a more restrictive preoperative benzodiazepine administration.

Evaluation of the drug-drug interaction potential of treosulfan using a physiologically-based pharmacokinetic modelling approach

AIMS

The aim of this work is the development of a mechanistic physiologically-based pharmacokinetic (PBPK) model using in vitro to in vivo extrapolation to conduct a drug-drug interaction (DDI) assessment of treosulfan against two cytochrome p450 (CYP) isoenzymes and P-glycoprotein (P-gp) substrates.

METHODS

A PBPK model for treosulfan was developed de novo based on literature and unpublished clinical data. The PBPK DDI analysis was conducted using the U.S. Food and Drug Administration (FDA) DDI index drugs (probe substrates) midazolam, omeprazole and digoxin for CYP3A4, CYP2C19 and P-gp, respectively. Qualified and documented PBPK models of the probe substrates have been adopted from an open-source online model database.

RESULTS

The PBPK model for treosulfan, based on both in vitro and in vivo data, was able to predict the plasma concentration-time profiles and exposure levels of treosulfan applied for a standard conditioning treatment. Medium and low potentials for DDI on CYP3A4 (maximum area under the concentration-time curve ratio (AUCRmax  = 2.23) and CYP2C19 (AUCRmax  = 1.6) were predicted, respectively, using probe substrates midazolam and omeprazole. Treosulfan was not predicted to cause a DDI on P-gp.

CONCLUSION

Medicinal products with a narrow therapeutic index (eg, digoxin) that are substrates for CYP3A4, CYP2C19 or P-gp should not be given during treatment with treosulfan. However, considering the comprehensive treosulfan-based conditioning treatment schedule and the respective pharmacokinetic properties of the concomitantly used drugs (eg, half-life), the potential for interaction on all evaluated mechanisms would be low (AUCR < 1.25), if concomitantly administered drugs are dosed either 2 hours before or 8 hours after the 2-hour intravenous infusion of treosulfan.

A Pharmacokinetic-Pharmacodynamic Study of Intravenous Midazolam and Flumazenil in Adult New Zealand White-Californian Rabbits (Oryctolagus cuniculus)

Flumazenil, a competitive GABAA receptor antagonist, is commonly used in rabbits to shorten sedation or postanesthetic recovery after benzodiazepine administration. However, no combined pharmacokinetic (PK) and pharmacodynamic (PD) data are available to guide its administration in this species. In a prospective, randomized, blinded, crossover study design, the efficacy of IV flumazenil (FLU; 0.05 mg/kg) or saline control (SAL; equal volume) to reverse the loss of righting reflex (LORR) induced by IV midazolam (1.2 mg/kg) was investigated in 15 New Zealand white rabbits (2.73 to 4.65 kg, 1 y old). Rabbits were instrumented with arterial (central auricular artery) and venous (marginal auricular vein) catheters. After baseline blood sampling, IV midazolam was injected (T0). Flumazenil or saline (FLU/SAL) was injected 30 s after LORR. Arterial blood samples were collected at 1 and 3 min after midazolam injection, and at 1, 3, 6, 10, 15, 21, 28, 36, 45 and 60 min after injection with flumazenil. Plasma samples for midazolam, 1-OH-midazolam and flumazenil were analyzed using high performance liquid chromatography-high-resolution mass spectrometry and the time to return of righting reflex (ReRR) was compared between groups (Wilcoxon test). FLU terminal half-life, plasma clearance and volume of distribution were 26.3 min [95%CI: 23.3 to 29.3], 18.74 mL/min/kg [16.47 to 21.00] and 0.63 L/kg [0.55 to 0.71], respectively. ReRR was 25 times faster in rabbits treated with FLU (23 [8 to 44] s) compared with SAL (576 [130 to 1141] s; 95%CI [425 to 914 s]). Return of sedation (lateral recumbency) occurred in both groups (7/13 in FLU; 12/13 in SAL) with return of LORR in a few animals (4/13 in FLU; 7/13 in SAL) at 1540 [858 to 2328] s. In the population and anesthesia protocol studied, flumazenil quickly and reliably reversed sedation induced by midazolam injection. However, the potential return of sedation after flumazenil administration warrants careful monitoring in the recovery period.

Pharmacokinetic study of midazolam and α-hydroxymidazolam in guinea pig blood and hair roots after a single dose of midazolam

The appearance of midazolam (M) and its metabolites into the hair root following a single administration was examined by following the time course of M and α-hydroxymidazolam (αHM) in hair roots and blood from guinea pigs. The back hair of guinea pigs was shaved before drug administration and before each sampling, and hair roots (3-5 mm) were plucked at 5, 15, and 30 min, 1, 2, 4, 6, 10, 24, 48, 72, 96, 120, 144 h, and 7, 14, 21, and 28 days. The kinetic parameters of M and αHM in guinea pig blood and hair roots were determined for three doses (5, 10, and 25 mg/kg). Comparisons of drug time course between hair roots and blood indicated an association between drug concentrations in the hair root and the blood. M and αHM entered the hair root within 5 min after a single exposure. The detection windows were also longer for the hair root than for the blood. Consequently, the hair root can be a valuable specimen in acute poisonings or drug-facilitated crime (DFC) cases, if other matrices are unavailable, or if blood and urine results are negative. Hair shafts (with hair roots) were plucked at 28 days and segmented. The concentrations of M and αHM were lower in the hair shafts than in the hair roots. The concentrations of the metabolite αHM in hair shafts were barely detectable. The concentrations of M and αHM in the hair root showed a moderate correlation with dose. Comparison of drug levels in hair roots between the washed group and the unwashed group indicated a generally stable percentage between the washed and unwashed groups of 40-60 % during the entire time course. This indicates that drugs are likely to be immobilized in the hair root at the beginning of the incorporation process.

Pre-operative Anxiety in Pediatric Surgery Patients: Multiple Case Study Analysis with Literature Review

Pre-operative anxiety affects millions of pediatric surgery patients each year and can have both short and long-term adverse effects in the post-operative period. As a result, it is particularly important for healthcare providers and others involved in the child's care, such as the parents, to be aware of interventions that can be used to reduce the onset of pre-operative anxiety and, thus, the likelihood of negative post-operative changes. The purpose of this paper is to familiarize the reader with the issue of pre-operative anxiety through a review of the literature and analysis of case studies. First, the paper looks at the causes of pre-operative anxiety and its effect on the development of maladaptive behavioral, emotional, and physiological changes. It then discusses the ways pre-operative anxiety can be measured and current methods for reducing the post-operative adverse outcomes associated with it. After doing so, it proposes the need for additional research and the use of precision medicine by physicians.

The Necessity of Using Changes in Absorption Time to Implicate Intestinal Transporter Involvement in Oral Drug-Drug Interactions

INTRODUCTION

In drug discovery and development, it is of high interest to characterize the potential for intestinal drug-drug interactions to alter bioavailability of a victim drug. For drugs that are substrates of both intestinal transporters and enzymes, estimating the relative contribution of each process has proved challenging, especially since the susceptibility of drug to uptake or efflux transporters in vitro does not always translate to clinically significant in vivo involvement. Here we introduce a powerful methodology to implicate intestinal transporters in drug-drug interactions based on the theory that clinically relevant intestinal transporter interactions will result in altered rate of absorption of victim drugs.

METHODS AND MATERIALS

We present exemplary clinical drug-drug interaction studies that utilize well-characterized clinical substrates and perpetrators to demonstrate how mean absorption time (MAT) and time to maximum concentration (t_max) are expected to change (or remain unchanged) when either intestinal transporters or metabolic enzymes were/are altered. Apixaban was also selected to demonstrate the utility of the methodology, as the purported involvement of both intestinal enzymes and transporters has been suggested in its FDA package insert.

RESULTS AND DISCUSSION

Acute inhibition of gut efflux transporters resulted in decreased MAT and t_maxvalues, induction increased these values, while inhibition of intestinal metabolic enzymes did not result in altered MAT or t_max. Involvement of intestinal efflux transporters in apixaban disposition is unlikely.

CONCLUSION

Utilization of this simple but powerful methodology to implicate intestinal transporter involvement will have significant impact on how drug-drug interactions are interpreted.

Propofol alone prevents worsening hepatic encephalopathy rather than midazolam alone or combined sedation after esophagogastroduodenoscopy in compensated or decompensated cirrhotic patients

BACKGROUND

This study was conducted to determine which type and dose of sedative drugs should be given to cirrhotic patients with compensation or decompensation during esophagogastroduodenoscopy (EGD) to prevent hepatic encephalopathy (HE) after sedation.

METHODS

We reviewed the medical records of cirrhotic patients consecutively admitted to the hospital and conducted a number connection test (NCT) before and 2 h after EGD with moderate sedation. Sedation was performed using either propofol alone, midazolam alone, or combined propofol + midazolam.

RESULTS

Sixty-seven patients were admitted for a screening EGD. The NCT before and after sedation were not significantly different in the propofol alone (pre-NCT = 47.3 ± 19.71 seconds vs. post-NCT = 49.4 ± 21.79 seconds, P = 0.6389). In the midazolam alone (pre-NCT = 50.3 ± 20.56 vs. post-NCT = 63.7 ± 33.17, P = 0.0021) and in the combined propofol + midazolam (pre-NCT = 47.4 ± 20.99 vs. post-NCT = 60.0 ± 30.79, P = 0.0002), NCT were significantly delayed. The propofol alone group received 52.3 ± 16.31 mg (0.82 ± 0.29 mg/kg). In 45 (67.2%) decompensated patients, only the propofol alone was not significantly different between pre-NCT (49.2 ± 22.92) and post-NCT (52.3 ± 24.90) (P = 0.4548). Serum sodium level was significantly correlated with delta-NCT (r = 0.3594, P = 0.0028).

CONCLUSION

Propofol alone could be the best sedation strategy for cirrhotic patients with compensation or decompensation without aggravation of covert or overt HE. Hyponatremia could be a risk factor for developing or worsening HE after EGD with sedation.

Tacrolimus blood concentration increase depends on administration route when combined with voriconazole in pediatric stem cell transplant recipients

BACKGROUND

Understanding of TAC pharmacokinetics is required to avoid both overdosing and underdosing. VRCZ is known to increase the TAC blood concentration by inhibiting CYP3A4; however, detailed, practical information on pediatric cases is still scarce. Herein, we investigated the association between the TAC blood concentration and dosage focusing on the administration route and concomitant use of VRCZ in children.

METHODS

In total, 38 children who received TAC during stem cell transplantation at our hospital between January 2013 and April 2018 were included. The ratio of the TAC blood concentration (ng/mL) to dosage (mg/kg/day) (C/D) was calculated at the last continuous intravenous infusion (C/Div) and after switching to oral administration (C/Dpo).

RESULTS

Patients with VRCZ (n = 14) showed a higher C/D regardless of administration route (median C/Div: with VRCZ/without VRCZ = 832/643, median C/Dpo: with VRCZ/without VRCZ = 339/45). Additionally, the (C/Div)/(C/Dpo) was about one-fourth in cases with VRCZ; the median (C/Div)/(C/Dpo) was 3.3 for cases with VRCZ and 13.5 for cases without VRCZ. Interestingly, the increase in the TAC blood concentration due to VRCZ was higher when TAC was administered orally, especially in adolescent patients.

CONCLUSIONS

To obtain an optimal TAC blood concentration, dose adjustment based on multiple factors, such as administration route, concomitant use of VRCZ, and age, is required.

[Drugs for intravenous induction of anesthesia: ketamine, midazolam and synopsis of current hypnotics]

Ketamine and midazolam form the endpoint of a series of articles about intravenous induction of anesthesia . Both substances can be used as single induction hypnotic drugs; however, in practice, this is unusual. Both substances, with the exception of a few very specific indications and clinical situations, are more frequently used in combination or with one of the more common alternatives propofol, barbiturates and etomidate. The reasons are the activity and side effects of both substances and their positive characteristics are used more as a supplement. In the concluding comparison the five discussed induction hypnotics are judged against each other. The use in certain clinical constellations and in special patient populations is evaluated individually for each substance. It is highlighted which drug appears most appropriate in which situation. As methohexital is nowadays only administered in very few clinical situations, this substance is not included in the comparative assessment.

Model qualification of the PK-Sim® pediatric module for pediatric exposure assessment of CYP450 metabolized compounds

Pediatric physiologically based pharmacokinetic (PBPK) models facilitate the estimation of pharmacokinetic (PK) parameters in children under specific exposure conditions. In human health risk assessment, PBPK modeling has been used to determine a chemical-specific human kinetic adjustment factor (HKAF). Due to increased demands in regulatory assessment, model evaluation and qualification have gained growing attention. The aim of this study was to undertake model qualification of pediatric PBPK models for compounds that are primarily metabolized by cytochrome P450 (CYP) enzymes. The objectives were to determine the appropriateness of the virtual individual creating algorithm in PK-Sim® in predicting PK parameters and their variability in children and identify critical system-specific inputs. PBPK models in adults were constructed for several pharmaceuticals (grouped by major clearance process such as CYP3A4). Several age groups of virtual individuals were created to represent children in pediatric clinical studies. The mean and variance of clearance (CL) from virtual populations were compared to observed values. Sensitivity analysis on area under the curve (AUC) was performed. System-specific parameters of virtual children that contribute to inter-individual PK properties were assessed. Eighty-one percent of the comparisons between simulated and observed clearance values were within twofold error. The mean fold errors were 1.1, 1, 0.7 and 1.8 in adolescents, children, infants and neonates, respectively. CL variability was reasonably predicted for 70% of the comparisons with comparable coefficients of variation between observed and predicted. The sensitivity analysis revealed that fraction unbound in plasma, parameters related to CYP enzyme-mediated metabolism and liver volumewere most important in the estimation of pediatric exposure. A comparison of variabilities in weight, height and liver volume in virtual children showed reliable agreement with observed data. The presented results of predictive performance and properties of virtual populations provide confidence in the use of PK-Sim for pediatric PBPK modeling in toxicological applications including PBPK-based-HKAF derivation.

Midazolam: Safety of use in palliative care: A systematic critical review

PURPOSE

The undesired effects of midazolam can be life-threatening. This paper delineates the findings related to the pharmacokinetics, adverse effects and drug-drug interactions as well as associated therapeutic implications for safe midazolam use.

METHODS

A systematic review of literature was conducted.

RESULTS

The pharmacokinetics of midazolam depends on hepatic and renal functions, fat tissue mass, route and duration of administration, as well as potential drug-drug interactions. Palliative care patients constitute a high-risk group prone to side effects of drugs, due to polytherapy and multi-organ failure.

CONCLUSION

Midazolam is one of three most frequently administered drugs in palliative care. The indications for its use include anxiety, dyspnea, seizures, vomiting refractory to treatment, agitation, myoclonus, status epilepticus, restlessness, delirium, pruritus, hiccups, insomnia, analgosedation, palliative sedation and preventing or counteracting undesired effects of ketamine.

CYP3A4-mediated effects of rifampicin on the pharmacokinetics of vilaprisan and its UGT1A1-mediated effects on bilirubin glucuronidation in humans

AIMS

The primary aim of the present study was to quantify the effects of rifampicin, a strong cytochrome P450 (CYP) 3A4 inducer, on the pharmacokinetics of the new selective progesterone receptor modulator, vilaprisan. In addition, the effects of rifampicin on the glucuronidation of bilirubin, an endogenous UDP-glucuronosyltransferase family 1 member A1 (UGT1A1) substrate, were explored.

METHODS

This was an open-label, two-period study in 12 healthy postmenopausal women. Subjects received a single oral dose of vilaprisan 4 mg in each period. In period 2, administration of vilaprisan was preceded and followed by rifampicin 600 mg day^-1 . A subtherapeutic dose of midazolam (1 mg) was coadministered with vilaprisan to monitor CYP3A4 induction. Details of the administration and sampling schedule were optimized by means of a physiologically based pharmacokinetic model. Plasma concentrations of vilaprisan, midazolam, and 1'- hydroxy-midazolam were measured and rifampicin-associated changes in the glucuronidation of bilirubin were determined.

RESULTS

As predicted by our model, the coadministration of rifampicin was associated with a substantial decrease in exposure to vilaprisan and midazolam - indicated by the following point estimates (90% confidence intervals) for the area under the plasma concentration-time curve from zero to the time of the last quantifiable concentration ratio with or without rifampicin: 0.040 (0.0325, 0.0505) for vilaprisan and 0.144 (0.117, 0.178) for midazolam. Further, it was associated with an increase in bilirubin glucuronidation, indicating that UGT1A1 was induced.

CONCLUSIONS

The exposure to vilaprisan was reduced by 96%. Such a reduction is likely to render the drug therapeutically ineffective. Therefore, it is recommended that the use of strong CYP3A4 inducers is avoided when taking vilaprisan.

A Two-way Randomized Cross-over Pharmacokinetic and Pharmacodynamic Study of an Innovative Oral Solution of Midazolam (ADV6209)

PURPOSE

The objective of this study was to assess the bioavailability and the sedative effect of a single-dose administration of an innovative oral solution of midazolam containing γ-cyclodextrins (ADV6209).

METHODS

A bioavailability study with a standard two-sequences, two-periods, and crossover design was conducted. Subjects randomly received 15 mg of ADV6209 by oral route followed by 5 mg of the reference drug (midazolam hydrochloride intravenous solution (Hypnovel®, Roche) by intravenous route or vice versa. Blood samples were drawn at different time points to measure midazolam and its metabolite α-hydroxymidazolam concentrations. Non-compartmental pharmacokinetic methods were used to calculate main pharmacokinetic parameters and absolute bioavailability.

RESULTS

Caucasian healthy subjects (n = 12) were included in the study. ADV6209 had a bioavailability of 39.6%. The oral elimination half-life with ADV6209 was slightly shorter than with the reference i.v. form (2.66 h versus 2.99 h). The sedative effect was observed 27.5 ± 15.5 min after oral administration for a duration of 48.5 ± 35.4 min. Double peak phenomenon was observed in 5 patients.

CONCLUSIONS

Cyclodextrins have little impact on midazolam oral bioavailability and the pharmacokinetics parameters of midazolam formulation ADV6209 are close to those reported previously.

Pharmacokinetics and pharmacodynamics of a new highly concentrated intranasal midazolam formulation for conscious sedation

AIM

To evaluate the pharmacokinetics, pharmacodynamics, nasal tolerance and effects on sedation of a highly concentrated aqueous intranasal midazolam formulation (Nazolam) and to compare these to intravenous midazolam.

METHODS

In this four-way crossover, double-blind, double-dummy, randomized, placebo-controlled study, 16 subjects received 2.5 mg Nazolam, 5.0 mg Nazolam, 2.5 mg intravenous midazolam or placebo on different occasions. Pharmacokinetics of midazolam and α-hydroxy-midazolam were characterized and related to outcome variables for sedation (saccadic peak velocity, the Bond and Lader visual analogue scale for sedation, the simple reaction time task and the observer's assessment of alertness/sedation). Nasal tolerance was evaluated through subject reporting, and ear, nose and throat examination.

RESULTS

Nazolam bioavailability was 75%. Maximal plasma concentrations of 31 ng ml^-1 (CV, 42.3%) were reached after 11 min (2.5 mg Nazolam), and of 66 ng ml^-1 (coefficient of variability, 31.5%) after 14 min (5.0 mg Nazolam). Nazolam displayed a significant effect on OAA/S scores. Sedation onset (based on SPV change) occurred 1 ± 0.7 min after administration of 2.5 mg intravenous midazolam, 7 ± 4.4 min after 2.5 mg Nazolam, and 4 ± 1.8 min after 5 mg Nazolam. Sedation duration was 118 ± 95.6 min for 2.5 mg intravenous midazolam, 76 ± 80.4 min for 2.5 mg Nazolam, and 145 ± 104.9 min for 5.0 mg Nazolam. Nazolam did not lead to nasal mucosa damage.

CONCLUSIONS

This study demonstrates the nasal tolerance, safety and efficacy of Nazolam. When considering the preparation time needed for obtaining venous access, conscious sedation can be achieved in the same time span as needed for intravenous midazolam. Nazolam may offer important advantages in conscious sedation.

Prevention and Intervention Strategies to Alleviate Preoperative Anxiety in Children

Preoperative anxiety (anxiety regarding impending surgical experience) in children is a common phenomenon that has been associated with a number of negative behaviors during the surgery experience (e.g., agitation, crying, spontaneous urination, and the need for physical restraint during anesthetic induction). Preoperative anxiety has also been associated with the display of a number of maladaptive behaviors postsurgery, including postoperative pain, sleeping disturbances, parent-child conflict, and separation anxiety. For these reasons, researchers have sought out interventions to treat or prevent childhood preoperative anxiety and possibly decrease the development of negative behaviors postsurgery. Such interventions include sedative premedication, parental presence during anesthetic induction, behavioral preparation programs, music therapy, and acupuncture. The present article reviews the existing research on the various modes of intervention for preoperative anxiety in children. Clinical implications and future directions are discussed.

Mechanistic Modeling to Predict Midazolam Metabolite Exposure from In Vitro Data

Methods to predict the pharmacokinetics of drugs in humans from in vitro data have been established, but corresponding methods to predict exposure to circulating metabolites are unproven. The objective of this study was to use in vitro methods combined with static and dynamic physiologically based pharmacokinetic (PBPK) models to predict metabolite exposures, using midazolam and its major metabolites as a test system. Intrinsic clearances (CLint) of formation of individual metabolites were determined using human liver microsomes. Metabolic CLintof hydroxymidazolam metabolites via oxidation and glucuronidation were also determined. Passive diffusion intrinsic clearances of hydroxymidazolam metabolites were determined using sandwich cultured human hepatocytes and the combination of this term along with the metabolic CLint, and liver blood flow was used to estimate the fraction of the metabolite that can enter the systemic circulation after formation in the liver. The metabolite/parent drug area under the plasma concentration-time curve ratio (AUCm/AUCp) was predicted using a static model relating the fraction of midazolam clearance to each metabolite, the clearance rates of midazolam and hydroxymidazolam metabolites, and the availability of the metabolites. Additionally, the human disposition of midazolam metabolites was simulated using a SimCYP PBPK model. Both approaches yielded AUCm/AUCpratios that were in agreement with the in vivo ratios. This study shows that in vivo midazolam metabolite exposure can be predicted from in vitro data and PBPK modeling. This study emphasized the importance of metabolite systemic availability from its tissue of formation, which remains a challenge to quantitative prediction.

Propofol versus midazolam for upper gastrointestinal endoscopy in cirrhotic patients: a meta-analysis of randomized controlled trials

BACKGROUND

Sedation during gastrointestinal endoscopy is often achieved using propofol or midazolam in general population. However, impaired protein synthesis, altered drug metabolism, and compromised hepatic blood flow in patients with liver cirrhosis might affect the pharmacokinetics of sedatives, placing cirrhotic patients undergoing endoscopy at a greater risk of adverse events. The objective of this study was to assess comparative efficacies and safety of propofol and midazolam in cirrhotic patients undergoing endoscopy.

METHODS

Randomized, controlled trials comparing propofol with midazolam in cirrhotic patients undergoing gastrointestinal endoscopy were selected. We performed the meta-analysis, using a random-effect model, the Review Manager, Version 5.2, statistical software package (Cochrane Collaboration, Oxford, UK) according to the PRISMA guidelines.

RESULTS

Five studies between 2003 and 2012, including 433 patients, were included. Propofol provided a shorter time to sedation (weight mean difference: -2.76 min, 95% confidence interval: -3.00 to -2.51) and a shorter recovery time (weight mean difference -6.17 min, 95% confidence interval: -6.81 to -5.54) than midazolam did. No intergroup difference in the incidence of hypotension, bradycardia, or hypoxemia was observed. Midazolam was associated with the deterioration of psychometric scores for a longer period than propofol.

CONCLUSION

This meta-analysis suggests that Propofol sedation for endoscopy provides more rapid sedation and recovery than midazolam does. The risk of sedation-related side effects for propofol does not differ significantly from that of midazolam. The efficacy of propofol in cirrhotic patients undergoing endoscopy is superior to those of midazolam.

Comparative pharmacokinetics and bioavailability of intranasal and rectal midazolam formulations relative to buccal administration in rabbits

The rectal and intranasal formulations under current development demonstrated comparative potential for administering midazolam in treating seizures in a medical emergency service.

Automated high-capacity on-line extraction and bioanalysis of dried blood spot samples using liquid chromatography/high-resolution accurate mass spectrometry

RATIONALE

Pharmacokinetic data to support clinical development of pharmaceuticals are routinely obtained from liquid plasma samples. The plasma samples require frozen shipment and storage and are extracted off-line from the liquid chromatography/tandem mass spectrometry (LC/MS/MS) systems. In contrast, the use of dried blood spot (DBS) sampling is an attractive alternative in part due to its benefits in microsampling as well as simpler sample storage and transport. However, from a practical aspect, sample extraction from DBS cards can be challenging as currently performed. The goal of this report was to integrate automated serial extraction of large numbers of DBS cards with on-line liquid chromatography/high-resolution accurate mass spectrometry (LC/HRAMS) bioanalysis.

METHODS

An automated system for direct DBS extraction coupled to a LC/HRAMS was employed for the quantification of midazolam (MDZ) and α-hydroxymidazolam (α-OHMDZ) in human blood. The target analytes were directly extracted from the DBS cards onto an on-line chromatographic guard column followed by HRAMS detection. No additional sample treatment was required. The automated DBS LC/HRAMS method was developed and validated, based on the measurement at the accurate mass-to-charge ratio of the target analytes to ensure specificity for the assay.

RESULTS

The automated DBS LC/HRAMS method analyzed a DBS sample within 2 min without the need for punching or additional off-line sample treatment. The fully automated analytical method was shown to be sensitive and selective over the concentration range of 5 to 2000 ng/mL. Intra- and inter-day precision and accuracy was less than 15% (less than 20% at the LLOQ). The validated method was successfully applied to measure MDZ and α-OHMDZ in an incurred human sample after a single 7.5 mg dose of MDZ.

CONCLUSIONS

The direct DBS LC/HRAMS method demonstrated successful implementation of automated DBS extraction and bioanalysis for MDZ and α-OHMDZ. This approach has the potential to promote workload reduction and sample throughput increase.

Midazolam pharmacokinetics in morbidly obese patients following semi-simultaneous oral and intravenous administration: a comparison with healthy volunteers

BACKGROUND

While in vitro and animal studies have shown reduced cytochrome P450 (CYP) 3A activity due to obesity, clinical studies in (morbidly) obese patients are scarce. As CYP3A activity may influence both clearance and oral bioavailability in a distinct manner, in this study the pharmacokinetics of the CYP3A substrate midazolam were evaluated after semi-simultaneous oral and intravenous administration in morbidly obese patients, and compared with healthy volunteers.

METHODS

Twenty morbidly obese patients [mean body weight 144 kg (range 112-186 kg) and mean body mass index 47 kg/m(2) (range 40-68 kg/m(2))] participated in the study. All patients received a midazolam 7.5 mg oral and 5 mg intravenous dose (separated by 159 ± 67 min) and per patient 22 samples over 11 h were collected. Data from 12 healthy volunteers were available for a population pharmacokinetic analysis using NONMEM(®).

RESULTS

In the three-compartment model in which oral absorption was characterized by a transit absorption model, population mean clearance (relative standard error %) was similar [0.36 (4 %) L/min], while oral bioavailability was 60 % (13 %) in morbidly obese patients versus 28 % (7 %) in healthy volunteers (P < 0.001). Central and peripheral volumes of distribution increased substantially with body weight (both P < 0.001) and absorption rate (transit rate constant) was lower in morbidly obese patients [0.057 (5 %) vs. 0.130 (14 %) min(-1), P < 0.001].

CONCLUSIONS

In morbidly obese patients, systemic clearance of midazolam is unchanged, while oral bioavailability is increased. Given the large increase in volumes of distribution, dose adaptations for intravenous midazolam should be considered. Further research should elucidate the exact physiological changes at intestinal and hepatic level contributing to these findings.

Issues in the management of acute agitation: how much current guidelines consider safety?

Agitated behavior constitutes up to 10% of emergency psychiatric interventions. Pharmacological tranquilization is often used as a valid treatment for agitation but a strong evidence base does not underpin it. Available literature shows different recommendations, supported by research data, theoretical considerations, or clinical experience. Rapid tranquilization (RT) is mainly based on parenteral drug treatment and the few existing guidelines on this topic, when suggesting the use of first generation antipsychotics and benzodiazepines, include drugs with questionable tolerability profile such as chlorpromazine, haloperidol, midazolam, and lorazepam. In order to systematically evaluate safety concerns related to the adoption of such guidelines, we reviewed them independently from principal diagnosis while examining tolerability data for suggested treatments. There is a growing evidence about safety profile of second generation antipsychotics for RT but further controlled studies providing definitive data in this area are urgently needed.

Bispectral index monitoring of midazolam sedation during flexible bronchoscopy

BACKGROUND

Flexible bronchoscopy could be an uncomfortable examination for some patients. The purpose of this study was to examine the patient characteristics associated with "patient satisfaction" with sedation during flexible bronchoscopy.

METHOD

Fifty-two patients undergoing diagnostic flexible bronchoscopy were divided into 2 groups. Group A (n=44) comprised patients who felt that the sedation was satisfactory, and group B (n=8) comprised patients who felt otherwise. All patients were given midazolam to maintain Ramsay sedation scores of 2 to 3. We measured blood pressure, heart rate, respiratory rate, oxygen saturation, and bispectral index scores (BIS) every 5 minutes during bronchoscopy. Adverse events were also recorded.

RESULTS

There were no significant differences between the 2 groups in terms of age, height, weight, blood pressure, heart rate, respiratory rate, oxygen saturation, duration of flexible bronchoscopy, or doses of lidocaine and midazolam. The BIS was significantly lower for group A than for group B. Adverse events that would lead to aborting the procedure were not encountered.

CONCLUSIONS

We suggest that the BIS value during flexible bronchoscopy is associated with the satisfaction of patients and they may be able to predict patients' satisfaction.

Randomized controlled trial for endoscopy with propofol versus midazolam on psychometric tests and critical flicker frequency in people with cirrhosis

BACKGROUND AND AIM

People with cirrhosis are at increased risk of development of complications related to sedation. The aim of the present study was to compare the effects of sedation for upper gastrointestinal endoscopy (UGIE) with propofol and midazolam on psychometric tests and critical flicker frequency (CFF) in people with cirrhosis.

METHODS

A total of 127 people with cirrhosis were randomized into three groups: propofol group (n = 40), midazolam group (n = 42) and no sedation (n = 45). All patients underwent CFF test and combination of psychometry (number connection test-A and B [NCT-A,B]; digit symbol test [DST], line tracing test [LTT] and serial dotting test [SDT]) at baseline and at 2 h post-endoscopy. CFF was done at 30 min and repeated every 30 min for 2 h.

RESULTS

In the propofol group there was no deterioration in psychometry (NCT-A [55.6 ± 18.7 vs 56.4 ± 19.0 s], NCT-B [98.2 ± 35.1 vs 97.8 ± 34.6 s], DST [26.7 ± 5.7 vs 26.3 ± 5.3], LTT [112.9 ± 35.7 vs 113.7 ± 36.6 s], SDT [94.6 ± 34.1 vs 95.2 ± 34.5 s]). Significant deterioration from baseline (39.8 ± 2.9 Hz) was seen in CFF at 30 min (38.8 ± 2.3 Hz) and 1 h (39.2 ± 2.4 Hz), P = 0.01 but no difference thereafter. In the midazolam group, significant deterioration was observed on psychometry (NCT-A [56.0 ± 18.5 vs 60.4 ± 19.8 s], NCT-B [99.9 ± 29.1 vs 105.9.6 ± 30.3 s], DST [26.1 ± 4.7 vs 25.2 ± 4.3], LTT [129.1 ± 34.5 vs 132.9 ± 35.4 s], SDT [95.6 ± 34.2]). No deterioration was observed in psychometry and CFF in people with cirrhosis without sedation.

CONCLUSIONS

Propofol sedation for UGIE was associated with earlier recovery compared with midazolam, which causes deterioration of psychometric tests and CFF for a longer time in comparison with propofol.

In vitro-in vivo extrapolation of clearance: modeling hepatic metabolic clearance of highly bound drugs and comparative assessment with existing calculation methods

In vitro-in vivo extrapolation (IVIVE) is an important method for estimating the hepatic metabolic clearance (CL) of drugs. This study highlights a problematic area observed when using microsomal data to predict in vivo CL of drugs that are highly bound to plasma proteins, and further explores mechanisms for human CL predictions by associating additional processes to IVIVE disconnect. Therefore, this study attempts to develop a novel IVIVE calculation method, which consists of adjusting the binding terms in a well-stirred liver model. A comparative assessment between the IVIVE method proposed here and previously published methods of Obach (1999. Drug Metab Dispos 27:1350-1359) and Berezhkovskiy (2010. J Pharm Sci 100:1167-1783) was also performed. The assessment was confined by the availability of measured in vitro and in vivo data in humans for 25 drugs highly bound to plasma proteins, for which it can be assumed that metabolism is the major route of elimination. Here, we argue that a difference in drug ionization and binding proteins such as albumin (AL) and alpha-1-acid glycoprotein (AAG) in plasma and liver also needs to be considered in IVIVE based on mechanistic studies. Therefore, converting unbound fraction in plasma to liver essentially increased the predicted CL values, which resulted in much more accurate estimates of in vivo CL as compared with the other IVIVE methods tested. The impact on CL estimate was more apparent for drugs binding to AL than to AAG. This is a mechanistic rational for explaining a considerable proportion of the divergence between previously estimated and observed CL values. Human CL was predicted within 1.5-fold, twofold, and threefold of the observed CL for 84%, 96%, and 100% of the compounds, respectively. Overall, this study demonstrates a significant improvement in the mechanism-based prediction of metabolic CL for these 25 highly bound drugs from in vitro data determined with microsomes, which should facilitate the application of physiologically based pharmacokinetic (PBPK) models in drug discovery and development.

Profound changes in drug metabolism enzymes and possible effects on drug therapy in neonates and children

INTRODUCTION

There are profound changes that take place in drug metabolism enzymes during fetal and postnatal development. These changes may significantly impact drug therapy in children.

AREAS COVERED

A combination of focused and comprehensive literature searches using PubMed and reference lists (from inception to 7 November 2009) is undertaken to identify reports on in vitro and in vivo development of drug metabolism enzymes as well disposition of selected drugs and their effect in children. The article provides an update on development of drug metabolism enzymes and their impact on drug substrate disposition and disease, which may aid to improve clinical practice and optimally design clinical trials in children.

EXPERT OPINION

Drug metabolism enzyme activity changes profoundly throughout the continuum of postnatal development and often results in different disposition pathways than in adults. Genetics and co-morbidity interact significantly with these developmental changes. Translation of existing knowledge into age-adjusted dosing guidelines and clinical trial design is highly needed for there to be an improvement in drug therapy in children.

Sub-clinical hepatic encephalopathy in cirrhotic patients is not aggravated by sedation with propofol compared to midazolam: a randomized controlled study

BACKGROUND & AIMS

The risk of exacerbating sub-clinical hepatic encephalopathy (HE) by propofol has not been established. The aim of this study is to determine whether the use of propofol, for upper endoscopy in patients with cirrhosis, precipitates sub-clinical HE.

METHODS

Sixty-one patients with compensated HCV and HBV cirrhosis (CP score 5-6) were randomly selected and divided into two groups (intent-to-treat population) matched for age, gender, and BMI. The first group received a single propofol sedation (N = 31, age 57 ± 12, dose range 70-100 mg/procedure) and the second group (N = 30, age 56 ± 12, dose 3-6 mg/procedure) received a single midazolam sedation, all done by an anesthesiologist. All patients completed number connection test (NCT), cognitive function score, time to recovery, time to discharge sheets, and hemodynamic parameters before sedation, and at discharge from the endoscopy unit, 1h post-procedure. Thirty control subjects without cirrhosis were matched to the cirrhotic patients who received sedation with regard to age, gender, BMI, and education level.

RESULTS

A total of 58/61 cirrhotic patients (95%) had sub-clinical encephalopathy before the endoscopy (mean NCT 84.7 ± 77 s, normal < 30 s). No patient developed overt HE after sedation. There were no differences between groups in the incidence of adverse effects, cognitive function, MELD score, CP score, oxygen saturation, or respiratory and heart rates before and after sedation. Propofol did not exacerbate minimal HE when compared to midazolam (NCT changed from 87.5 ± 62 s prior to sedation to 74.2 ± 58 s after sedation in the propofol group versus 72.8 ± 62 s before to 85.6 ± 72 s after sedation in the midazolam group; p < 0.01). Time to recovery (4.1 ± 1.9 min vs. 11.5 ± 5.0 min, p < 0.001), and time to discharge (38.0 ± 9 min vs. 110 ± 42 min, p < 0.001) were significantly shorter with propofol than midazolam. Pre- and post-procedure NCT (from 25 ± 20 s to 24 ± 20 s), cognitive function score (from 25 to 26), time to recovery (3.5 ± 1.0 min), and time to discharge (35 ± 10 min) did not change in the healthy controls.

CONCLUSIONS

Sedation with propofol has a shorter time recovery and a shorter time to discharge than midazolam and does not exacerbate sub-clinical hepatic encephalopathy in patients with compensated liver cirrhosis.

Effects of oral clotrimazole troches on the pharmacokinetics of oral and intravenous midazolam

AIMS

The aim of the study was to determine the effects of oral clotrimazole troches on the pharmacokinetics of oral and intravenous midazolam in the plasma.

METHODS

We conducted a randomized, open-label, four-way crossover study in 10 healthy volunteers. Each volunteer received oral midazolam 2 mg or intravenous midazolam 0.025 mg kg(-1) with and without oral clotrimazole troches 10 mg taken three times daily for 5 days. Each study period was separated by 14 days. Serial blood samples were collected up to 24 h after oral midazolam and 6 h after intravenous midazolam. Plasma concentrations for midazolam and its metabolite 1-hydroxymidazolam were measured and fitted to a noncompartmental model to estimate the pharmacokinetic parameters.

RESULTS

Ten healthy volunteers aged 21-26 years provided written informed consent and were enrolled into the study. Clotrimazole decreased the apparent oral clearance of midazolam from 57 +/- 13 l h(-1)[95% confidence interval 48, 66] to 36 +/- 9.8 l h(-1) (95% confidence interval 29, 43) (P= 0.003). These changes were accompanied by a decrease in the area under the concentration-time curve (mean difference 22 microg h(-1) l(-1), P= 0.001) and bioavailability (mean difference 0.21, P= NS). There were no significant differences in the systemic clearance of midazolam with or without clotrimazole troches.

CONCLUSIONS

Oral clotrimazole troches decreased the apparent oral clearance of midazolam; no significant differences in the systemic clearance of midazolam were found.

A review of the clinical pharmacokinetics of opioids, benzodiazepines, and antimigraine drugs delivered intranasally

BACKGROUND

Interest in the development of drug-delivery devices that might improve treatment compliance is growing. A dosage formulation that is easy to use, such as intranasal application with transmucosal absorption, may offer advantages compared with other routes of drug delivery. The literature concerning intranasal application is diffuse, with a large number of published studies on this topic. Some cerebroactive pharmaceuticals delivered intranasally might follow the pathway from the nose to the systemic circulation to the brain. To determine the suitability of these drugs for intranasal drug delivery, a systematic review was performed.

OBJECTIVE

The aim of this review was to compare the pharmacokinetic properties of intranasal, intravenous, and oral formulations in 3 classes of cerebroactive drugs that might be suitable for intranasal delivery-opioids, benzodiazepines, and antimigraine agents.

METHODS

A search of MEDLINE, PubMed, Cumulative Index of Nursing and Allied Health Literature, EMBASE, and Cochrane Database of Systematic Reviews (dates: 1964-April 2009) was conducted for pharmacokinetic studies of drugs that might be suitable for intranasal delivery. A comparison of pharmacokinetic data was made between these 3 routes of administration.

RESULTS

A total of 45 studies were included in this review. Most of the opioids formulated as an intranasal spray reached a T(max) within 25 minutes. The bioavailability of intranasal opioids was high; in general, >50% compared with opioids administered intravenously. Intranasal benzodiazepines had an overall T(max) that varied from 10 to 25 minutes, and bioavailability was between 38% and 98%. T(max) for most intranasal antimigraine drugs varied from 25 to 90 minutes. Intranasal bioavailability varied from 5% to 40%.

CONCLUSIONS

This review found that intranasal administration of all 3 classes of drugs was suitable for indications of rapid delivery, and that the pharmacokinetic properties differed between the intranasal, oral, and intravenous formulations (intravenous > intranasal > oral).

Current cytochrome P450 phenotyping methods applied to metabolic drug-drug interaction prediction in dogs

Recombinant cytochrome P450 (P450) phenotyping, different approaches for estimating fraction metabolized (f(m)), and multiple measures of in vivo inhibitor exposure were tested for their ability to predict drug interaction magnitude in dogs. In previous reports, midazolam-ketoconazole interaction studies in dogs have been attributed to inhibition of CYP3A pathways. However, in vitro phenotyping studies demonstrated higher apparent intrinsic clearances (CL(int,app)) of midazolam with canine CYP2B11 and CYP2C21. Application of activity correction factors and isoform hepatic abundance to liver microsome CL(int,app) values further implicated CYP2B11 (f(m) >or= 0.89) as the dog enzyme responsible for midazolam- and temazepam-ketoconazole interactions in vivo. Mean area under the curve (AUC) in the presence of the inhibitor/AUC ratios from intravenous and oral midazolam interaction studies were predicted well with unbound K(i) and estimates of unbound hepatic inlet inhibitor concentrations and intestinal metabolism using the AUC-competitive inhibitor relationship. No interactions were observed in vivo with bufuralol, although significant interactions with bufuralol were predicted with fluoxetine via CYP2D and CYP2C pathways (>2.45-fold) but not with clomipramine (<2-fold). The minor caffeine-fluvoxamine interaction (1.78-fold) was slightly higher than predicted values based on determination of a moderate f(m) value for CYP1A1, although CYP1A2 may also be involved in caffeine metabolism. The findings suggest promise for in vitro approaches to drug interaction assessment in dogs, but they also highlight the need to identify improved substrate and inhibitor probes for canine P450s.

Pregnancy does not increase CYP3A or P-glycoprotein activity in the non-human primate, Macaca nemestrina

Plasma concentrations of protease inhibitors are lower in pregnant women than in nonpregnant women or men. Using nelfinavir as a model protease inhibitor, we have shown that this phenomenon can be reproduced in a representative non-human primate model, Macaca nemestrina (J Pharmacol Exp Ther 329:1016-1022, 2009). Nelfinavir is cleared from the body predominantly by CYP3A metabolism and P-glycoprotein (P-gp) efflux. Therefore, using midazolam (MDZ) as a CYP3A probe and digoxin (DIG) as a P-gp probe, we determined the antepartum (73-118 days) and postpartum (61-130 days) in vivo intestinal and hepatic CYP3A or P-gp activity in the macaque. Although the systemic clearance of MDZ was significantly increased ( approximately 70%) during pregnancy after intra-arterial (IA) administration of the drug ((15)N-labeled MDZ; 40 microg/kg), pregnancy did not affect the oral clearance of the drug administered simultaneously (1 mg/kg p.o.) with the IA dose. In vitro studies in hepatic and intestinal S-9 fractions indicated no effect of pregnancy on CYP3A activity or protein expression in the small intestine or liver. In contrast, neither the oral (100 microg/kg) nor the IA (10 microg/kg) clearance of DIG was significantly altered by pregnancy, indicating no effect of pregnancy on P-gp activity. Assuming that MDZ and DIG are selective substrates of the macaque CYP3A enzymes and P-gp, respectively, these results suggest that factors other than increased CYP3A or P-gp activity contribute to the increased clearance of protease inhibitors during M. nemestrina pregnancy.

Pharmacodynamic and pharmacokinetic effects of the intravenously administered CB1 receptor agonist Org 28611 in healthy male volunteers

CB1/CB2 agonists are reported to have sedative, amnestic, analgesic and anti-emetic properties, which would make them ideal drugs for outpatient treatments under conscious sedation. The main objective of this in human study was to assess the sedative properties of Org 28611, a potent water-soluble CB1 agonist. Single ascending doses were administered during a slow 25 min infusion and after a 1 min bolus administration to healthy male volunteers. In addition, the pharmacokinetics, amnestic properties, postural stability, electro-encephalography, behavioural and cardiovascular effects were studied. Midazolam 0.1 mg/kg was used as a positive control. The pharmacokinetic parameters were proportional to dose. No effects were observed after intravenous administration of doses up to Org 28611 1 microg/kg. Dose-related effects were observed at higher doses. Although subjects reported subjective sedation after administration of Org 28611 3-10 microg/kg, the observed sedation was considerably less than after midazolam. Org 28611 is, therefore, not suitable for providing sedation for outpatient surgical procedures and doses above the maximum tolerated dose of 3 microg/kg (either administered as a slow infusion or a bolus dose) can cause untoward psychotropic effects.

Identification of a cranberry juice product that inhibits enteric CYP3A-mediated first-pass metabolism in humans

An in vivo study in rats showed a cranberry juice product to inhibit the intestinal first-pass metabolism of the CYP3A substrate nifedipine. However, a clinical study involving the CYP3A probe substrate midazolam and a different cranberry juice product showed no interaction. Because the composition of bioactive components in natural products can vary substantially, a systematic in vitro-in vivo approach was taken to identify a cranberry juice capable of inhibiting enteric CYP3A in humans. First, the effects of five cranberry juices, coded A through E, were evaluated on midazolam 1'-hydroxylation activity in human intestinal microsomes. Juice E was the most potent, ablating activity at 0.5% juice (v/v) relative to control. Second, juice E was fractionated to generate hexane-, chloroform-, butanol-, and aqueous-soluble fractions. The hexane- and chloroform-soluble fractions at 50 microg/ml were the most potent, inhibiting by 77 and 63%, respectively, suggesting that the CYP3A inhibitors reside largely in these more lipophilic fractions. Finally, juice E was evaluated on the oral pharmacokinetics of midazolam in 16 healthy volunteers. Relative to water, juice E significantly increased the geometric mean area under the curve (AUC)(0-infinity) of midazolam by approximately 30% (p=0.001), decreased the geometric mean 1'-hydroxymidazolam/midazolam AUC(0-infinity) ratio by approximately 40% (p<0.001), and had no effect on geometric mean terminal half-life, indicating inhibition of enteric, but not hepatic, CYP3A-mediated first-pass metabolism of midazolam. This approach both showed a potential drug interaction liability with cranberry juice and substantiated that rigorous in vitro characterization of dietary substances is required before initiation of clinical drug-diet interaction studies.